2008 – Plunge pool design at Gebidem Dam (Switzerland)
Erik Bollaert, Nicola Bretz
Abstract: Gebidem Dam is a 122 m high double curvature arch dam situated in the canton of Wallis, Switzerland. The dam reservoir collects glacier water of the longest glacier in Europe, i.e. the Aletsch glacier (25 km length). The water is very rich in sediment. This results in huge amounts of fine sediments depositing into the reservoir. The 55 m3/s turbined by the Bitsch power station contain between 10 and 13 kg of sand, or an average of almost 40 tons per hour.
Hence, a yearly flushing is organized allowing to release about 400’000 m3 of solid material from the bottom outlets of the dam towards downstream. Moreover, the crest spillway of the dam is frequently used during summer months to release water from the reservoir, resulting in high-velocity jets impacting the downstream plunge pool. The latter consists of a series of flat concrete plates tied together by means of steel anchors and supported by a layer of underlying mass concrete.
Intensive jet impact on this concrete apron within the last 40 years has led to severe damage and, as such, replacement of the apron becomes necessary. The present paper describes the methodology applied for design of a new concrete apron. Especially the interaction between the hydrodynamic pressures exerted by overtopping jets and the steel anchorage necessary to prevent uplift of the new concrete apron is pointed out.
Keywords: scour, concrete apron design, anchorage
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Papers 2008
2008 – Inelastic seismic analysis of Dartmouth Intake Tower
Learn moreFrancisco Lopez, John Bosler
Abstract: A study has been undertaken to determine the structural adequacy of the Intake Tower for the Dartmouth Dam Low Level Outlet Works under the Maximum Design Earthquake (MDE). The tower is a reinforced concrete frame structure. The study included the definition of appropriate seismic inputs and nonlinear time-history analyses for different levels of ground shaking.
The behaviour of the tower was assessed in terms of material strains. The seismic acceleration-time history was applied to the model and the nonlinear analysis identified the locations in the structure which reached the following performance thresholds: cracking of core concrete, yielding of reinforcing steel, fracture of reinforcing steel and crushing of core concrete.
The results of the study showed that the tower was able to resist, without collapse, the loadings imposed by three different MDE acceleration time-histories. The predicted level of damage consisted of generalised yielding of reinforcement, formation of numerous plastic hinges at different locations in the tower and generalised spalling of cover concrete.
Overall, the structural response of the tower under the MDE events was considered satisfactory and met the performance requirement that structural collapse should not occur.
Keywords: intake tower, nonlinear, inelastic, time-history, seismic analysis.
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Papers 2008
2008 – Construction of the first cut-off wall by Low Headroom Cutter inside a dam tunnel in China
Learn moreBrunner Wolfgang G, Bi Arthur, Chang William, Zong Dung Feng
ABSTRACT: In the South of the Sichuan province the 240 MW Yeleh hydroelectric power project is under construction by Sichuan Nanya River Basin Hydraulic Power Development Company Limited, a state-owned enterprise, and China Gezhou Ba Water & Power Group Company Ltd.. This project sets out to develop the mountain cascade of the Nanya river, a tributary of the Dadu River, provide superior electricity and adjust flood peak and frequency. The specialist contractor Foundation Engineering Company of China Water Resource and Hydropower (FEC) was awarded the contract of foundation treatment at the right bank, which included the construction of a 75 m deep concrete cut-off wall inside a 6.0 m x 6.5 m tunnel. The requirement for 19 317 m3 cut-off wall to be constructed in permeable and very dense gravel/cobble formations and a demanding project program led FEC to adopt the BAUER Low Headroom Cutter CBC25/MBC30 in conjunction with the overlap cutter joint.
Keywords: hydroelectric project, dam, dam tunnel, cut-off wall, trench cutter
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Papers 2008
2008 – Improving confidence in computational fluid dynamics for spillways
Learn moreRichard John Kenny
Abstract: Physical hydraulic models have traditionally provided the input to spillway design.
However, the application of Computational Fluid Dynamics (CFD) is increasing in popularity.
The reliability of CFD depends on several complex issues including the physics of the flow regime, the mathematical formulae describing the fluid flow and the solution method. CFD reliability should be confirmed for each particular application, including ogee spillways (common discharge structures on dams).A literature review has been undertaken to determine validation techniques and the reliability of CFD related to ogee spillways. There is a great deal of information available about the aeronautical, marine, automotive and mining industries but relatively little available about ogee spillways. The degree of validation for ogee spillways was found to vary significantly and raises the question of whether better validation can be achieved. Better validation may improve confidence in CFD techniques.
A project has been undertaken through Queensland University of Technology to model a prototype scale notional 2D ogee spillway using FLUENT CFD software under steady state conditions. The project tests the sensitivity of the CFD results to various parameters. The sensitivity of the inlet mass flow rate was tested for several CFD parameters. The investigation considered:
1.The grid spacing required for geometric convergence;
2.The effect of domain extent on the computational results;
3.The influence of a boundary layer and wall roughness;
4.The importance of the choice of turbulence model; and
5.The impact of inlet turbulence assumptions.
The recommendations of the sensitivity investigations were used for validation against the United States Army Corp of Engineers (USACE) design data.
Excellent agreement was found between the CFD predictions and the USACE values.
Keywords: Computational fluid dynamics (CFD), dam, flood routing, fluent, Navier-Stokes equations, Numerical/computational modelling, Ogee spillway crest, physical model, turbulence.
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Papers 2008
2008 – Implementing upstream fish passage at an existing large dam: Hinze Dam trap and haul fishway
Learn moreSteven O’Brien, Brent Mefford, John Harris
Abstract: The Hinze Dam Stage 3 Upgrade required ‘Waterway Barrier Works Approval’, including fish-passage assessments. The dam, sited in the Nerang River catchment, has relatively undisturbed riverine habitat upstream which, together with the reservoir’s recreational fishery, was a key driver for inclusion of a fishway. Low outflows from the dam and impacts of development on the river downstream contrast starkly with upstream environments.
The Hinze Dam Alliance (HDA) assessed that upstream transfer of fish will have significant environmental benefits but downstream passage, beyond that achieved during spill events, could not be justified.
Constraints at the site for upstream passage include unvarying 7.25ML/d releases from the reservoir and a distance of nearly 300m between the reservoir and the downstream river pool. HDA has developed an innovative trap-and-haul system to collect upstream-migrating fish near the spillway and transport them by tanker to upstream release areas. This system is the first of its kind designed for Australia. It provides flexibility to accommodate varying fish biomass, the ability to operate over a range of flows up to 20-year ARI events, facilities for data collection and removal of pest species, and capacity to manage predation with small-fish refuges during trapping and transfer and by releasing fish at several protected sites in the reservoir.
Keywords: fishway, trap and haul System, fish passage
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Papers 2008
2008 – Securing water for growth in regional Queensland
Learn moreTim Donaghy
Abstract: Queensland’s regions need additional water supply infrastructure to underpin the future economic growth of the state, and secure the water supplies of existing communities in light of climate variability.
Queensland’s economy has consistently been the fastest growing of all the States for the last decade. The major component of Queensland’s growth is underpinned by resources and industry, in regional areas of the State. If the enabling infrastructure is absent, or if timeframes for development do not align with the needs of the industry, this growth will be constrained, or will go elsewhere. Future investments that support growth cannot and will not occur without certainty around the availability of future water supply.
Queensland’s regions are emerging from the worst drought in recorded history, this has revealed serious deficiencies in the resilience of our regional water supplies. For the first time in living memory, major regional centres have been forced to face the prospect of running out of water.
The Queensland Government has been proactive in identifying these issues and has responded resolutely through the release of Statewide Water Policy which supports a $451 million investment in regional water infrastructure, which aims to meet the needs of urban and rural users.As part of this policy SunWater has been named proponent for a range of projects considered essential for Queensland’s future economic sustainability which include the Nathan Dam on the Dawson River, Water for Bowen & Proserpine Pipeline Projects, Rookwood Weir & Eden Bann Weir Raising (with RRC & GAWB), Connors River Dam & Pipelines, Nullinga Dam and Kinchant Dam Raising. SunWater is also investigating the raising of Queensland’s largest dam, Burdekin Dam. This paper will outline the need for water supply infrastructure within regional Queensland, and the challenges faced by the projects being progressed by SunWater including the technical issues, environmental sustainability and approvals, and commercial development challenges.
Keywords: Queensland, Water Supply Infrastructure, Dams
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